Direct torque control (DTC) which replaces the conventional current loop with torque loop can directly control the electromagnetic torque in order to reduce the torque error within the hysteresis bandwidth, and it can attenuated commutation torque ripple and the torque ripple of brushless DC (BLDC) motor with un-ideal back electromotive force (EMF) waveforms. Further, the key issue of feedback torque calculation in torque loop is the estimation of back-EMF in sensorless DTC of BLDC motor. So a sliding mode observer (SMO) is employed to estimate the back-EMF in real time. The torque and rotor speed can be derived from the estimated back-EMF. Simulation results demonstrate the proposed method is valid and effective.
Torque ripple suppression of brushless DC motor drives using an alternating two‐phase and three‐phase conduction mode